∫∠DBC = 45，

∴db=cd=x,ad=x+4.5；

In Rt△ACD, tan∠A=,

∴tan35 =；

Solution: x =10.5;

So the height of the big tree is 10.5 meters.

Solution 2: In Rt△ACD, tan∠A=, ∴ AD =;

In Rt△BCD, tan∠CBD=, ∴ BD =;

AD﹣BD=4.5, that is ﹣ =4.5,

Solution: CD =10.5;

So the height of the big tree is 10.5 meters.